GR already posted for PO & (final delivery indicator set)

What causes this issue?

The goods receipt has been fully posted for the purchase order. You
cannot post a further goods receipt for the purchase order. The
"delivery complete" indicator has been set for the purchase order
either manually or as a result of a system setting.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Goods receipt for purchase order already posted:
Delete goods receipt item (Press F6 to not post GR)
Post GR for another purchase order:
Select purchase orders (Press Shift+F6 to select POs)
Post GR for a PO created subsequently:
Create PO and GR (Press F8 to create PO/GR)

Error message extract from SAP system. Copyright SAP SE.